Reversible ratchet wrenches are well known and are commonly sold in a wide variety of sizes. However, regardless of size or available features, all such ratchet wrenches may generally be classified as one of two types: the round head ratchet wrench, or the pear (oval) head ratchet wrench. Under either classification such a ratchet wrench will possess several similar characteristics such as: the ability to transfer torque from the wrench handle to a fastener; the ability to ratchet when the wrench handle is rotated in the opposite direction; the capability of reversing the direction of the torque and ratcheting strokes; and a means for attachment to sockets, extensions, and other drive tools.
A round head ratchet wrench is generally smaller in size than a pear head ratchet wrench, and thus may better fit into tighter workspaces. A ratchet wrench generally has a handle for transmitting torque, and a housing that contains the moving, internal parts of the ratchet mechanism. In a round head ratchet wrench, teeth are often formed around the inner circumference of the housing. A reversible pawl is commonly employed in such a wrench. The pawl is generally designed to engage the housing teeth during rotation of the wrench handle in one direction, while allowing the pawl to ratchet across the housing teeth during rotation of the wrench handle in the opposite direction.
In a pear head ratchet wrench, a toothed drive wheel is generally utilized to engage a reversible pawl, providing torque transmission in one direction and ratcheting in the other direction. The main disadvantage of the pear head ratchet wrench is its housing size. Additionally, the components of a pear head ratchet wrench and the components of a round head ratchet wrench are not generally interchangeable.
A serious disadvantage of both types of ratchet wrenches is the limited number of pawl teeth that generally engage the housing teeth or drive wheel teeth respectively. When fewer teeth are engaged, there is less total shear area available across the teeth to resist the forces resulting from the torque applied to the wrench handle. As a consequence of such design, high stress levels are placed on the individual teeth that are engaged. To accommodate these high stress levels, the internal components of the ratchet wrench are often fabricated from expensive, exotic materials that generally require heat treating to achieve the necessary strength and durability.
One aspect of the present invention is to provide a reversible ratchet wrench wherein a majority, or, preferably all of the pawl teeth are engaged during the torque-transmitting stroke of the wrench. Engagement of the whole of the pawl teeth with either the housing teeth or the drive wheel teeth respectively, distributes the shear forces over a larger area, reducing the stresses on the individual teeth. This design permits a reduction in individual component size, which allows for a reduction in overall housing size. Additionally, because the individual teeth are no longer required to endure such high stress levels, the components may be produced from more conventional and less costly materials.
Another aspect of the present invention is to produce a round head ratchet wrench and a pear head ratchet wrench that can utilize a substantial number of common components. Such a situation would be advantageous due to the reduction in required individual components, and the reduced costs associated therewith.
The present invention contemplates both a round head and a pear head reversible ratchet wrench employing two pawls of preferably conical shape, for transmitting operator applied torque from the wrench handle to the fastener.
A round head reversible ratchet wrench is provided in one embodiment of the present invention. In a preferred embodiment, the round head reversible ratchet wrench has a handle, which may be permanently or removably affixed to a housing of substantially round shape. The housing is provided to contain the internal, moving parts of the wrench, which are preferably held together by means of a retaining screw. Teeth are formed around the inner circumference of the housing for engaging one of two pawls. One end of a main drive is inserted through the first pawl and into the housing. The other end of the main drive may be releasably attached to sockets, extensions, or other drive tools. A second pawl is inserted into the other side of the housing. A selector is provided for reversing the ratcheting direction of the wrench. Rotating the selector brings one pawl into engagement with the teeth in one side of the housing, while simultaneously releasing the other pawl from engagement with the teeth in the other side of the housing.
An important feature of the round head reversible ratchet wrench of the present invention is that the shape of the pawls and the housing allows for engagement of all the teeth on a respective pawl when the pawl is in contact with the housing. Engagement of all the pawl teeth, with the housing teeth, allows the forces exerted on the pawl to be distributed across all of the pawl teeth, thereby reducing the stress levels on each individual tooth.
In another embodiment of the present invention, a pear head reversible ratchet wrench is contemplated. In a preferred embodiment, the pear head reversible ratchet wrench has a handle that may be permanently or removably affixed to a housing. The configuration of the housing in this embodiment of the invention is referred to in the art as "pear shaped." The housing is provided to contain the internal, moving parts of the wrench. Teeth are formed around the inner circumference of the housing for engaging each one of two pawls. One end of a main drive is inserted through the first pawl and into the housing. The other end of the main drive may be releasably attached to sockets, extensions, or other drive tools. A second pawl is inserted into the other side of the housing. A shifter is located in the housing for reversing the ratcheting direction of the wrench. The shifter is designed to allow a button to protrude from one of either sides of the housing. Pressing one side of the button shifter brings one pawl into engagement with the teeth in one side of the housing, while simultaneously releasing the second pawl from engagement with the teeth in the other side of the housing. Pressing the opposite side of the button shifter will reverse the position of the respective pawls.
An important feature of the reversible pear head ratchet wrench of the present invention is that the shape of the pawls and the housing allows for engagement of all the teeth on a respective pawl when the pawl is in contact with the housing. Engagement of all the pawl teeth with the housing teeth allows the forces exerted on the pawl to be distributed across all of the pawl teeth, thereby reducing the stress levels on each individual tooth.